NativeAOT doesn't work with Linux non-portable build

[agocke]

The problem is that NativeAOT references OpenSSL in two different ways, depending on whether we're doing a portable build or not.

When portable, the Native AOT runtime uses lazy loading (dlopen) to load the installed OpenSSL shared library. This means that the final linking command for a Native AOT app doesn't need the OpenSSL dev shared library to be passed when linking, since it will not try to statically resolve symbols.

This is not true for non-portable builds. In this case, Native AOT is built directly against OpenSSL headers/SOs. This means that Native AOT apps have to pass the appropriate SO to the linker during final linking of NativeAOT apps.

This means that the linking of Native AOT apps depends on whether it was originally compiled with a portable build. We could also try to remove this difference at the root by choosing one way to reference OpenSSL consistently.

More broadly, the feature of a "non-portable" AOT build is questionable. This would produce a Native AOT compiler which can only compiler for the exact platform (e.g. Ubuntu 22.04) that the compiler was built for. This is generally an anti-pattern in compilers.

[omajid]

How does NativeAOT deal with bundled/system library split? source-build can be built so that it uses the system version of libunwind or the version included in runtime under src/native/external. Is that something else that needs to be tracked here?

[jkotas]

In source build, NativeAOT is built directly against OpenSSL headers/SOs. This means that NativeAOT apps have to pass the appropriate SO to the linker during final linking of NativeAOT apps.

All native dependencies are referenced directly in source build. We would need to do this for icu, gssapi, zlib, brotli, and potentially also libunwind that @omajid mentioned above.

[jkotas]

Not required for 7.0: dotnet/source-build#2885 (comment)

[crummel]

I've summarized what I believe to be the current state of play and the agreed-upon solution for NativeAOT in 7.0 in #76206. Please check this out and let me know if you have any concerns.

[jkoritzinsky]

To expand on this, the flag here is actually controlled by if the build is portable, not necessarily source-build (it's possible to build a non-portable regular build and easier to do locally).

[jkotas]

We still have TODO comments linked to this issue https://github.com/search?q=repo%3Adotnet%2Fruntime%20https%3A%2F%2Fgithub.com%2Fdotnet%2Fruntime%2Fissues%2F66859&type=code , so I assume this should stay open?

[jkotas]

#97521 has discussion about the fix

[agocke]

Yup, this was a mistake, I meant to close #97521

[tmds]

I think that - thanks to the managed ObjWriter by @filipnavara! - this is the main thing that still needs to be solved to enable NativeAOT for source-build.

We need something that enables the linker flags to be different for non-portable builds.

Based on how we made source-build capable of doing SCD publish, I assume the flags would be stored in a rid-specific pack/package/folder. That is: the flags for portable would be in something linux-x64, and the flags for a distro-specific source-build would be in something fedora.39-x64.

A user then has these options:

• (using a portable rid for) building a portable NativeAOT app (leveraging nuget.org Microsoft binaries)
• (using a non-portable rid for) building a non-portable NativeAOT app (using distro binaries)

This first app is meant to work across a range of distros, and the second app is meant to meet the requirements for being included in a distro package (because all binaries used were built from source).

cc @dotnet/distro-maintainers

[jkotas]

We need something that enables the linker flags to be different for non-portable build

Take a look at #97536 . With this change, /p:PortableBuild=false build is going to produce native aot packages with distro specific RID. PublishAot with these packages is going to pass additional options to linker to produce distro specific binary.

[jkotas]

The last place that needs fixing is:

runtime/src/coreclr/tools/aot/ILCompiler/ILCompiler.csproj

Lines 13 to 14 in 7f02aef

	<!-- Can't use NativeAOT in source build yet https://github.com/dotnet/runtime/issues/66859 -->
	<NativeAotSupported Condition="'$(DotNetBuildFromSource)' == 'true'">false</NativeAotSupported>

. We should wait for the LKG SDK to pickup changes from #97536 first.

[jkotas]

I am reverting part of the change in #98303 to fix build break in source build. There is a confusion between the portable RID, non-portable RID and host RID.

@tmds Could you please take a look if you get a chance?

[tmds]

Sure, I'll take a closer look.

[tmds]

I will be looking into this next week.